The primary objective of this study is to compare conventional ventilation therapy to partial liquid ventilation as measured by changes in blood gas values (Pa02, PaC02, BE) and pulmonary function during the acute and extended intervention periods. The secondary objective is to have the investigators report time to death or discharge from the ICU after beginning of liquid installation. The number of survivors will be reported as well. Two infants have been enrolled thus far, one less than 1 kg and the other less than 2 kg. Both patients were randomized to partial liquid ventilation. Both had dramatic respiratory improvement within 4 hours after starting therapy. The only side effect was transient hypersecretion which occurred either late into the course of therapy or after therapy was discontinued.